Radio frequency thermal isolator

Abstract

A radio frequency (RF) thermal isolator and method of manufacture for same. According to one embodiment, the RF thermal isolator includes a first transmission line; a second transmission line of nominally the same dimensions as the first transmission line and axially aligned with the first transmission line, wherein the ends of the transmission lines are separated by a gap having a width that is a very small fraction of the center operating wavelength of the transmission lines; and an electrically conductive sleeve electrically attached to the end of the first transmission line and surrounding the end of the second transmission line and separated from the second transmission line by a gap having a width that is a very small fraction of the center operating wavelength of the transmission lines; wherein the sleeve extends along the second transmission line from the end of the first transmission line for a distance of nominally ¼ of the center operating wavelength of the transmission lines.

What is claimed is:  
     
       1. A radio frequency (RF) thermal isolator, comprising: 
       a first transmission line having an operating frequency;  
       a second transmission line having the operating frequency and being axially aligned with the first transmission line, wherein the first and second transmission lines have respective ends, the respective ends separated from each other by a first hollow gap; and  
       an electrically conductive sleeve electrically coupled to the end of the first transmission line and positioned about the end of the second transmission line, the electrically conductive sleeve being separated from the second transmission line by a second hollow gap, the second hollow gap being axially aligned with the second transmission line and extending continuously from the surface of the second transmission line to bottom of the sleeve.  
     
     
       2. The RF thermal isolator of  claim 1 , wherein each of the transmission lines is a respective waveguide. 
     
     
       3. The RF thermal isolator of  claim 1 , wherein each of the transmission lines is a respective coaxial cable having a respective inner conductor and a respective outer conductor, further comprising: 
       an inner conductor extension extending axially from the inner conductor of the first transmission line into a cavity in the inner conductor of the second transmission line, wherein the inner conductor extension of the first transmission line extends beyond the end of the first transmission line for a length that is substantially ¼ of the center operating wavelength at the operating frequency of the first and second transmission lines;  
       wherein the cavity extends into the inner conductor of second transmission line for a distance substantially ½ of the center operating wavelength at the operating frequency of the first and second transmission lines.  
     
     
       4. The RF thermal isolator of  claim 3 , wherein the respective inner conductors of the transmission lines are hollow, and vented with respect to each other and to the exterior of the RF thermal isolator. 
     
     
       5. The RF thermal isolator of  claim 1 , wherein the transmission lines and sleeve are comprised of a conductive metal. 
     
     
       6. The RF thermal isolator of  claim 1 , wherein the transmission lines and sleeve are comprised of a composite material coated with a metallic layer. 
     
     
       7. The RF thermal isolator of  claim 1 , further comprising: 
       a mechanical coupler attached between the transmission lines.  
     
     
       8. The RF thermal isolator of  claim 1 , wherein the first hollow gap and the second hollow gap each have a width that is nominally {fraction (1/100)} of the center of the operating wavelength at the operating frequency. 
     
     
       9. The RF thermal isolator according to  claim 1 , wherein the first hollow gap and the second hollow gap thermally isolate heat transmission between the first and second transmission lines. 
     
     
       10. The RF thermal isolator of  claim 1 , wherein the first hollow gap has a width that is a very small fraction of a center operating wavelength at the operating frequency. 
     
     
       11. The RF thermal isolator of  claim 1 , wherein the second hollow gap has a width that is a very small fraction of a center operating wavelength at the operating frequency. 
     
     
       12. The RF thermal isolator of  claim 1 , wherein the sleeve extends along the second transmission line for a distance that is about ¼ of the center operating wavelength at the operating frequency. 
     
     
       13. The RF thermal isolator of  claim 1 , wherein the first transmission line has a first temperature and the second transmission line has a second temperature different than the first temperature. 
     
     
       14. A method comprising: 
       electrically coupling an electricity conductive sleeve upon the outer surface of a first transmission line, the first transmission line having an operating frequency; and  
       disposing an end of a second transmission line having the operating frequency within the sleeve such that the second transmission line is axially aligned with the first transmission line and the ends of the first and second transmission lines are separated by a first hollow gap;  
       wherein the sleeve is positioned about the end of the second transmission line, the sleeve being separated from the second transmission line by a second hollow gap, the second hollow gap being axially aligned with the second transmission line and extending continuously from the surface of the second transmission line to bottom of the sleeve.  
     
     
       15. The method of  claim 14 , further comprising: fabricating the transmission lines and sleeve from a conductive metal. 
     
     
       16. The method of  claim 14 , further comprising: fabricating the transmission lines and sleeve from a composite material coated with a metallic layer. 
     
     
       17. The method of  claim 14 , wherein the first transmission line has a first temperature and the second transmission line has a second temperature different than the first temperature. 
     
     
       18. The method of  claim 14 , wherein the first hollow gap and the second hollow gap each have a width that is nominally {fraction (1/100)} of the center of the operating wavelength at the operating frequency. 
     
     
       19. A product made by the process of  claim 14 . 
     
     
       20. The method of  claim 14 , wherein each of the transmission lines is a respective coaxial cable having a respective inner conductor and a respective outer conductor, further comprising: 
       forming a cavity in the inner conductor of the second transmission line, the cavity having a length of substantially ½ of the center operating wavelength at the operating frequency of the first and second transmission lines; and  
       mounting an inner conductor extension upon the inner conductor of the first transmission line such that the inner conductor extension extends axially from the inner conductor of the first transmission line into the cavity in the inner conductor of the second transmission line, wherein the center conductor of the first transmission line extends beyond the end of the first transmission line for a length that is substantially ¼ of the center operating wavelength at the operating frequency of the first and second transmission lines.  
     
     
       21. A product made by the process of  claim 20 . 
     
     
       22. The method of  claim 20 , wherein the respective inner conductors of the transmission lines are hollow, further comprising: venting the respective inner conductors of the transmission lines with respect to each other and to the exterior of the RF thermal isolator. 
     
     
       23. The method of  claim 14 , wherein the first hollow gap and the second hollow gap thermally isolate heat transmission between the first and the second transmission lines. 
     
     
       24. The method of  claim 14 , wherein each of the transmission lines is a respective waveguide. 
     
     
       25. A product made by the process of  claim 24 . 
     
     
       26. The method of  claim 14 , wherein the second hollow gap has a width that is a very small fraction of a center operating wavelength at the operating frequency. 
     
     
       27. The method of  claim 14 , wherein the first hollow gap has a width that is a very small fraction of a center operating wavelength at the operating frequency. 
     
     
       28. The method of  claim 14 , wherein the sleeve extends beyond an end of the first transmission line for a distance that is about ¼ of the center operating wavelength at the operating frequency. 
     
     
       29. The method of  claim 14 , further comprising: 
       mounting a mechanical coupler between the first and second transmission lines.  
     
     
       30. The method of  claim 29 , wherein the step of mounting a mechanical coupler between the transmission lines comprises: 
       mounting a mechanical coupler between the sleeve and the second transmission line.  
     
     
       31. The method of  claim 30 , wherein the step of mounting a mechanical coupler between the transmission lines comprises: 
       mounting a retainer upon the second transmission line; and  
       mounting a mechanical coupler between the sleeve and the retainer.